Corrosion inhibitor



Patented Sept. 22,

conaosrou mnmrron Delton B. Frey, East Cleveland, and Albert R. Smith,Shaker Heights, Ohio, asslgnors to The Lubri-Zol Corporation, Wlcklifle,Ohio, a corporation of Ohio 3N0 m-swingf Application October 14, 1939,Serial No. 299,570

29 Claims- (Cl. 252-46) This invention relates particularly to corrosioninhibitors and. more-especially to the use of a material which undervarious environments has been found tobe particularly efiective for thepurpose of inhibiting corrosion of metallic surr faces such, forexample, as iron.

,It is a principal object of this inventiorr to provide a corrosioninhibitor which is effective under a wide variety of conditions formetallic surfaces generally, and which is particularly 'effective withiron or ferrous surfaces. Other objects of this invention will appear asthe description proceeds. r

To the accomplishment of the foregoing and relate ends, the invention,then, comprises the features hereinafter fully described, andparticularly pointed out in the claims, the following descriptionsetting forth in detail certain illustrative embodiments of theinvention, these being indicativevhowever of but a few of the variousways in which the principle of the invention may be employed.

Broadly stated, this inventioncomprises the use as a corrosion inhibitorof benzyl thio cyanate.

- The corrosion inhibiting properties of benzyl thio cyanate may beutilized in a variety of enwith benzyl thio cyanate. Protective films ofa non-drying character applied to a metallic surface may alsoadvantageously contain this corrosion inhibitor. Thus the oily filmwhich is applied to metallic articles for the purpose of preact withmetallic surfaces with which the lubricant comes in contact, and whichhave a tendency to cause corrosion of such surfaces.

In commercial lubricants this inclusion of materials, the corrosivenessof which is inhibited by benzyl thio cyanate, may be inadvertent orunavoidable as by the accidental remainder in the composition ofmaterials employed in refining processes or by the presence in the oilbase of materials which occur naturally therein, and which; it is eitherinexpedient or for other reasons not desirable to remove.

Examples of such inclusions are the traces of solvents and the likeemployed in the refining of mineral oil and the inclusions in mineraloil of naturally occurring materials in minor amounts which have atendency to be corrosive to metallic surfaces such as iron.

- Still a further-and perhaps the most valuable use of benzyl thiocyanate as a corrosion inhibitor is in lubricating compositions to whichare intentionallyadded, for various purposes, materials which haveeither as their primary or purely collateral property the ability toreact with the cated in such away as to either retain a thin serving thesame against corrosion during or subsequent to fabrication willadvantageously contain small amounts of this inhibitor. 7

It will thus be seen that this inhibitor is effective whether used in adrying oil base such as in paints, varnishes and lacquers, or in anon-drying oil base such as mineral oil. The principal field ofusefulness of benzyl thio cyanate as a corrosion inhibitor is in thefield oflubricants in which an oily body is employed as the lubricant,but which may contain accidental or intentional inclusions of materialswhich will chemically re- 5 bearing surfaces for the purpose ofimparting film of oil between such surfaces under conditions of extremepressures, or to provide an antifluxing film between such surfaces whichis effective toprevent actual metal to metal contact andconsequentseizure and scoring under conditions of extreme pressures. Compounds ofchlorine or sulfur or both as well as the intentional inclusion in thecomposition of elemental sulfur in solution are examples of extremepressure adadded to lubricating compositions for purposes other than toimpart extreme pressure char acteristics, but which are of such a naturethat they do react with metals such as iron. Examples of this class ofaddition agents are pour point,

depressors, inhibitors of sludge, and addition agents which lendoiliness to the composition.

The materials which impart improved oiliness to lubricating compositionsare generally oxygenbearing organic compounds. played in conjunctionwith extreme pressure addition agents of the character previouslydefined, in many cases have an auxiliary eflectyof activating theextreme pressure addition? agents. Benzyl thio cyanate is, therefore,-particularly suited for use as a corrosion inhibitor in lubricatingcompositions which -include 'a material capabio of reacting with themetallic surfaces being lubricated and an organic oxygen compound,especially when the latter-is of the type which, as indicated, willactivate the former.

Halogenated or more specifically chlorinated aliphatic compounds aregenerally less stable and more reactive with metal surfaces than are thehalogenated or more specifically chlorinated ring compounds. the use ofbenzyl thio cyanate with both types of halogen compounds, its greaterfield of usefulness will be found when employed in conjunction with thealiphatic halogen compounds. The ring type halogen compounds with whichthis inhibitor may be employed in combination are those, for example,disclosed in United States Patent No. 1,986,651. Inasmuch as thepresence of oxygen, either in separate compound or in the same moleculewith the halogen, in general has an activating influence on the halogen,the present inhibitor may be used to advantage in combination withextreme pressure addition agents of the type disclosed in United StatesPatent No. 2,137,- 782 to which patent reference may be had for a 1 listof specific examples of such compounds.

Halogen bearing aliphatic esters, acids and salts are examples of themore reactive type of halogen bearing addition agents with which thisinhibitor may be used with great advantage.

In certain instances the particular extreme pressure addition agent isproduced from a naturally occurring material since these are usuallymore generally available and thus can be These, when em- While thisinvention contemplates produced at a lower cost than pure compounds.

The naturally occurring materials such as sulfur containing orsulfurized petroleum fractions, or more particularly halogenated orchlorinated petroleum fractions such as mineral oil, foots oil,kerosene, paraffin wax are examples of materials of this character.Benzyl thio cyanate has been found to be particularlyefiective as acorrosion inhibitor when employed in combination with the latter classof materials in lubricating compositions generally.

Examples of sulfur bearing extreme pressure addition agents in additionto elemental sulfur as above defined, are the organic sulphides,polysulphides, mercaptans, thio acids, thio esters, etc., used either asthe only extreme pressure addition agent or in combination with anotherextreme pressure addition agent such as an organic halogen compound.This combination is particularly effective since it has beendemonstrated that these two classes of extreme pressure addition agentshave a cooperative effect.

Lubricating compositions made in accordance with the present inventionmay include as the only addition agents, those named, or more generallymay also include materials previously identified as oiliness agents suchas, for example, those which may be produced by the oxidation ofpetroleum fractions. The oxidized petroleum fractions are generallyfound useful as the oiliness material employed in a composition or thecharacter to which this invention relates, since the nature of theirsource makes them particularly compatible with and eflective incompositions in which the base is mineral oil.

The concentrations in which benzyl thio cyanate is employed as aninhibitor will depend, of course, upon the type of composition in whichit is incorporated and the use for which such composition is designed.For all of the above uses, however, and especially where an oil vehicleis employed whether of the drying or non-drying type, but particularlywhen the base of the composition is a non-drying oil, the inhibitor willbe employed in amounts of from about .005% to .5%. For use inlubricating compositions of the character above referred to generallysatisfactory results will be secured by the employment of the inhibitorin amounts of from about .01% to about 2%.

It is understood, of course, that when reference is had herein to acompounded lubricating composition including benzyl thio cyanate as acorrosion inhibitor, the base of such composition may be any suitablelubricating oil which in most instances will be a refined mineraloil-refined to the extent necessary to suit the 011 base to theparticular service for which it is designed. Similarly the additionagents should be oil soluble at least to the extent to which they arerequired to be present and sumciently non-volatile so that they will notbe driven off from the compositions at the temperatures encountered inservice. In

general this a requirement is met by addition agentswhichhave a vaporpressure less than atmospheric at a temperature of C. or preferably at atemperature of C. Compositions of this character generally comprise amajor proportion of mineral lubricating oil and minor amounts of theaddition agents named along with the inhibitor in the proportions abovespecified. When a concentrate is made to be blended with mineral oils,then, of course, the percentages, within which the various additionagents including the inhibitor may be present, will be correspondinglygreater depending upon the extent to which the concentrate is to bediluted in the manufacture of the finished product.

Benzyl thio cyanate is particularly effective as a corrosion inhibitorin the presence of moisture and especially so in instances where thecorresive effect of the primary corrosive constituent is eitheraugmented or produced entirely by the presence of moisture.

For the above reasons benzyl thio cyanate has particular usefulness inlubricating compositions blues and the like:

- aaoaass which c ntain'water-as a part of the normal en- 'vironme t orwith which water may accidentally come in contact. Examples of theformer are lubricants such as, are usedin reciprocating steam I engines.steam turbines,.boiler pumpsa'nd the like; andexamples of the latter arelubricants used in gear bones and gear cases such as difrerentials andtransmissions of automobiles.

The following is a, specific example of a lubricating composition whichwould be useful for the latter purpose:

Gear lubricant r ler cent Chlorinated pawas (40% Cl).... 8 Dibenzyldisulphide 215 Benzyl thio cyanete 0.1

The remainder being substantially all S. A. E. 90 mineral gear oil,viscosity about 85 sec. 8. U; S.

at 210 11, which may also contain such other addition agents as aresometimes employedin this type of composition.

\ The following is a specific example of a lubricating composition whichmay be advantageously employed in the presence of large quantities ofwater at high temperatures such as in steam tur- Turbine lubricant 1 Percent An extreme pressure addition agent-such as hexachlor diphenyloxide. 1 An oxidation inhibitor such as tri(methyi cyclohewllphosphitehenzyl thio cyanate; -si .1

Per cent Ortho-dichlor benzene 0.3 Hexachlor diphenyl oxide -V 0.3Tri(methyl-cyclohexy)phosphite 0.06 Benzyl thio cyanate 0.05

and the remainder being substantially all a highly q I or higher, and aviscosity of about 300 B. U. S. at 100' l l Motor oils for use in thecrankcases of internal combustion engines are also subject tocontamination with moisture and may therefore be beneilted by includingsmall amounts of benzyl thio cyanate as a corro'sion inhibitor. Anexample of a motor oil for this purpose is as follows:

crankcase lubricant J ler cent Methyl chlorsalicylate 0.2 Benzyl thiocyanate 0.05

the remainder being substantially all a. highly refined 3. A. E. minerallubricating oil having a viscosity of about 300 S. U. S. at 100 E,

= which may also contain such other addition agents as are sometimesemployed in this type of composition.

As previously indicated. benzyl thio cyanatc is particularly eflectiveas a corrosion inhibitor where the metallic surfaces are iron,accounting for the great utility of this material in the class ofcompositions above referred to- As an example of the corrosioninhibiting effect of benzyllthio cyanate, reference may be had to thefollowing laboratory tests by which 4 hits efiectiveness s a corrosioninhibitor may be rather accurately determined.

The test procedure is as follows:

A l x 2 in. strip of 24 gauge low carbon steel (8. All. 1015-1020)polished with emery cloth, is drilled in the center with a #19 drill,and the diagonally opposite corners bent at an angle of about 15 along aline extending from one corner to the center of the opposite long side.The strip 1 isaccurately weighed on an analytical balance.

refined S. A. E. 20 mineral lubricating oil having a viscosity of about300 S.'U. S at-.100 FL, which may also contain such other additionagents as are sometimes employed in this type of composition. i

Anctherclass of compositions in which benzyl thio cyanate may beemployed to advantage as a Hydraulic oil Per cent Ortho-dlchlor benzene0.4 Hexachlor diphenyl oxide i 0.4 Methyl stearate s 0.4 Benzyl thiocyanate 0.1

the remainder being substantially. all a highly refined mineral oilhaving a viscosity of from 200 to 500 S. U. S. at 100 F., and preferablyhaving a viscosity index (Dean and Davis) ofabout 100 This test piece isthen attached to the lower end of a 5" steel, (drill rod) shaft. The endof the shaft is threaded to take an 8-32 nut, and the test piece is heldbetween two nuts (machine steel). 5 cc. of distilled water is added to300 cc. of the oil, placed in a 400 cc. beaker. The

beaker is heated by means of a water bath at a temperature of 200 F. andagitated by rotating the steel shaft at 500 to 750 R. P. M., with theshaft held in position centered with the beaker and so that the steelstrip is about 1' above the bottom of the beaker. The test is continuedfor 24 hours. The steel strip is then removed, washed with benzol, andwiped clean with a dry cloth. The loss-in weight of the steel strip isdetermined and its appearance observed.

The following results were obtained with this procedure:

Test piece Num- Percent Composition Grams loss Appear- A in weight once1 Commercial hypoid 0 .001 Rusty.

gear lubricant. 2 SameasNo.i .05 .00l Norust. 3 Experimental hypoid 0.015 Rusty.

gear lubricant. 4.... Same m No. 3 .10 .004 No rust. 5.-- Experimentalhypoid 0 .02) Rusty. gear lubricant. 6 Same as No. 6 i0 .illl No rust.7.-- Experimental hypoid ,0 .025 Rusty.

gear lubricant. 8...-.. Same as No 7 10 .000 No rust.

rod bearings of internal combustion engines, for.

example lead-bronze.

. agitator.

The following laboratory test method has been i used to indicate thedegree of such corrosion:

A piece of lead-bronze metal, one cm. square and about i mini-.1 thickis suspended from a.

glass hook in e100 cc. Grimn low form beaker mcontaining between 70 and.80 cc.-o the oil inquestion. The beaker isplaced in an oven main-gtalned at a temperatureoi' 150 (2.31 C. tor 192 @hours- The test pieceis removediromthe oil,-

washed in benzene, then washedin naphtha and The following results wereobtained with this procedure:

-,Benzyl thio cyanate maybe prepared byany oi the well-known methods forpreparing alkyl or aryl thio cyanates, for example the following:

Equal molecular amounts of N'aCNS sand-- benzyl chloride were placed ina reaction vessel equipped with reflux condenser and a mechanical Thereaction vessel was heated by a- I of refined mineral lubricating 011containing.

. minor amount of benzyl thio cyanate. s

bath maintained at a temperature of 175? C. The

time of heating was. one hour. During this time,

the temperature must notexceed 180 C. After heating for 1 hour at 175 C.the reactants were We therefore particularly point out'and dis- 2. Alubricating composition comprising a maior proportion of lubricating oiland'from about .005% to about 5% of benzyl thio cyanata 3. The method ofimproving the characteristics of a lubricating oil composition tomaterially reduce itstendency to be corrosive to metallic surfaces whichcomprises admixing therewitha small amount of benzyl thio cyanate.

Percent loss No. Composition Percent in weight of BTC testpieoa i. an.E. 40 Pennsylvania motor 7 oil containing .5% oi the monodichior-stearote of ethylene glycol 0 .68

2. Same as No.1 .05 .3- S. A. E. 10 Pennsylv is or oil containing .25%methyl chlorsallcyiate 0 .38 4.. Some ssNn. has .29

5 '8. A. E. 10 Pennsylvania motor 1 i 7 oil containing .75% oi a mixtureof methyl and ethyl dichlor steal-ates 0 86 6 Same as No.5 .05 .36

organic, compound, having a vapor pressure less than atmospheric at 140C., a minor amount of, an oil soluble, organic-oxygen compound, and acooled at 150? C. and 5%.by weight, of solid anhydrous NazCOa wereadded. The reactants and NazCO; were agitated for 1 hour; no heat wasapplied during this time.

After agitating with Nazcoa, a vacuum was applied to the reaction vesseland the products distilled at an absolute pressure of 12 min. of

Hg. All materials distilling below 125 C. were discarded. All materialsdistilling between the temperatures of 125 and 135 C. were collected asbenzyl thiocyanate.

Instead of benzyl chloride, benzyl sulfate may be used and potassiumthiocyanate substituted for sodium. Care should be exercised in carryingout the reaction and purification of the product to prevent the productfrom being exposed to high temperatures, say 180 C. or more, since thethiocyanates are easily converted to isothiocyanates at such elevatedtemperatures.

The characteristics of typical preparations follow:

Melting point (2.-.. 341- 3d Boiling point C1760 mm.-- 231-233 Sulfurpercent 20.5

The term "benzyl thiocyanate as used herein is intended to apply to theproduct obtained as indicated above or by any satisfactory commercialprocess as well as to the chemically pure compound.

Other modes of applying "the principles of our invention may beemployed, change being made as regards the details described providedthe feetures stated in any of the following claims, or th eouivalent oisuch, be employed.

surfaces being lubricated, and 2 benzyl' minor :amount'of benzyl thiocyanate.

4. The method of improving the characteris-- tics of a refined mineraloil oiiecting its use as an extreme pressure lubricant 'whichcompri'sesadmixing therewith small amounts of both an addition agent capable ofreacting with the metallic cyanate. s s .5. The method of improving thecharacteristics of a refined mineral oil aflecting its use as alubricantwhich comprises admixing therewitha minor-amount of an oilsolublehalogen bearing organic compound, havinga vapor pressure lessthan atmospheric at 14090., and a minor amount of benzyl thio cyanate.

minor amount of. an oilsoluble: halogen bearing 7. A lubricatingcomposition comprising a base about .005 to about .5% of-benzyl thiocyanate.

9. An extreme pressure lubricating composition comprising a majorproportion of lubricating oil with the properties of such compositionaffecting its use as an extreme pressure lubricant improved byincorporating therein minor amounts, based on the amount of lubricatingoil, of an addition agent capable of reacting with the metallic surfacesbeing lubricated, and benzyl thio cyanate.

10. An extreme pressure lubricating composition comprising a majorproportion of lubricating oil with the properties of such compositionaffecting its use as an extreme pressure lubricant improved byincorporating therein minor amounts, based on the amount of lubricatingoil, of an addition agent having a vapor pressure loss than atmosphericat C., and capable of reacting with the metallic surfaces beinglubricated, and from about .005% to about 5% of benzyl thio cyanate.

11. A lubricating composition comprising a major proportion of mineraloil and minor proportions of a halogenated organic ring compound, andbenzyl thio cyanate.

3.2. A lubricating composition comprising a major proportion of mineraloil and minor proportions of a halogenated aliphatic compound, andbenzyl thio cyanate.

13. A lubricating composition comprising a major proportion of minerallubricating oil, and minor proportions of a halogenated organic comthio' 1 portions of a halogenated petroleum fraction,

an organic sulphur compound and benzyl thio cyanate.

16. The method of inhibiting corrosion ot a 1 metalisurface othe subjectto chcal action which comprises treating such surface with benzyltblocranate.

17. The method of inhibiting corrosion oi an iron surface otherwisesubject to coal sction which comprises treating such surface with benzylthiocyanste.

is. The method or inhibiting corrosion of a metal suriace otherwisesubject to coal ac= tion which comprises treating such'suriace with a.minor amount of benzyl thiocyte in an organic solvent,

19. The method of inhibiting corrosion of an iron surface otherwisesubject to chemical action which comprises treating such surfac with aminor amount oi benwi thlocyanate in e mineral oil.

20. As a new composition of matter n concentrate for use in lubricatingcompositions compris= ing in combination an addition agent caps ofreacting with metallic surfaces, and benzyl thiccyanate.

21. As a new composition oi matter e concentrate for use in lubricatingcompositions comprising in combtion an extreme pressure addition agenthaving it vapor pr rs less t atmospheric at 14c" C. and capable of chresc= tion with an iron surface, and benml e te.

22. An eirtr pressure lubricating composition comprising a or proportionoi lubrlca oil with the properties or such composition aflecting its useas an out pressure lubricant improved by incorpora therein minor amountsbased on the amount or lubricating oil or an addition agent cable ofreacting with an iron suriace. and benzyl thiocyanate.

23. As a new comtion or matter, a concentrate for use in lubricatingcompositions comp in comblnanon a major proportion ofcn organic additionngent capable or reacting with metallic surfaces, such addition agentcontaining sulphur and a halogen, and a minor amount of benzyl.thiocyanate. I

24. As a new composition of matter, a concentrate for use' inlubricating compositions comprising in combination a major proportion ofan organic addition agent capable of reacting with metallic surfaces,such addition agent comprising an organic halogen compound, and a minoramount or benzyl thiocyanate.

25. As a new composition of matter, a concentrate for use in lubricatingcompositions comprising in combination armajor proportion of an organicaddition agent capable of reacting with metallic surfaces, such additionagent comprising an organic halogencompound and an organic sulphurcompound, and a minor amount of benzyl thiocyanate.

26. As a new composition of matter, a concentrate for use in lubricatingcompositions comprising in combination a major proportion of en organicaddition agent capable of reacting with metallic surfaces, such additionagent comprising an organic halogen compound and an organicpolysulphide, and a minor amount or benzyl thiocyanete;

2'3. As a new composition ofmatter, a concentrate for use in lubricatingcompositions comprising in combination a major proportion of an organicaddition agent capable of reacting with metallic surfaces, such additionagent comprising an organic halogen compound and an arcmatic disulphide,and a minor amount of benzyl thiecyanete.

28. As a. new composition of matter, a concentrate for usein lubricatingcompositions com prising in combination a major proportion of, anorganic addition agent capable of reacting with metallic surfaces, suchaddition agent comprising chlorinated par wax and an aromaticdisulphide, and a minor amount oi benzyl thiocyanate.

29. As a new composition of matter, a concentrate for use in lubricatingcompositions comprising in combination a major proportion of ansulphide, and a minor amount of benzyl thiocyanate.

DEL'I'ON n. m. mun-rm sum.

